Abstract
IntroductionIn combined posterior–anterior stabilization of thoracolumbar burst fractures, the expandable vertebral body replacement device (VBRD) is typically placed bisegmentally for anterior column reconstruction (ACR). The aim of this study, however, was to assess feasibility, outcome and potential pitfalls of monosegmental ACR using a VBRD. In addition, clinical and radiological outcome of monosegmental ACR was related to that of bisegmental ACR using the same thoracoscopic technique.MethodsThirty-seven consecutive neurologically intact patients with burst fractures of the thoracolumbar junction (T11–L2) treated by combined posterior–anterior stabilization were included. Monosegmental ACR was performed in 18 and bisegmental ACR in 19 patients. Fracture type and extent of vertebral body comminution were determined on preoperative CT scans. Monosegmental and bisegmental kyphosis angles were analyzed preoperatively, postoperatively and at final radiological follow-up. Clinical outcome was assessed after a minimum of 2 years (74 ± 45 months; range 24–154; follow-up rate 89.2%) using VAS Spine Score, RMDQ, ODI and WHOQOL-BREF.ResultsMonosegmental ACR resulted in a mean monosegmental and bisegmental surgical correction of − 15.6 ± 7.7° and − 14.7 ± 8.1°, respectively. Postoperative monosegmental and bisegmental loss of correction averaged 2.7 ± 2.7° and 5.2 ± 3.7°, respectively. Two surgical pitfalls of monosegmental ACR were identified: VBRD positioning (1) onto the weak cancellous bone (too far cranially to the inferior endplate of the fractured vertebra) and (2) onto a significantly compromised inferior endplate with at least two (even subtle) fracture lines. Ignoring these pitfalls resulted in VBRD subsidence in five cases. When relating the clinical and radiological outcome of monosegmental ACR to that of bisegmental ACR, no significant differences were found, except for frequency of VBRD subsidence (5 vs. 0, P = 0.02) and bisegmental loss of correction (5.2 ± 3.7° vs. 2.6 ± 2.5°, P = 0.022). After exclusion of cases with VBRD subsidence, the latter did not reach significance anymore (4.9 ± 4.0° vs. 2.6 ± 2.5°, P = 0.084).ConclusionsThis study indicates that monosegmental ACR using a VBRD is feasible in thoracolumbar burst fractures if the inferior endplate is intact (incomplete burst fractures) or features only a single simple split fracture line (burst-split fractures). If the two identified pitfalls are avoided, monosegmental ACR may be a viable alternative to bisegmental ACR in selected thoracolumbar burst fractures to spare a motion segment and to reduce the distance for bony fusion.
Highlights
In combined posterior–anterior stabilization of thoracolumbar burst fractures, the expandable vertebral body replacement device (VBRD) is typically placed bisegmentally for anterior column reconstruction (ACR)
Inclusion criteria were defined as follows: (1) burst fracture of the vertebral body of the thoracolumbar junction (T11–L2) treated by combined posterior–anterior stabilization with mono- or bisegmental ACR using an expandable VBRD (SynexTM, Synthes Inc., Bettlach, Switzerland or Hydrolift®, Aesculap AG, Tuttlingen, Germany); (2) age > 18 and < 65 years; and (3) absence of neurological deficits [American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade E]
The degree of vertebral body injury classified according to the AOSpine Thoracolumbar Spine Injury Classification System [A3 vs. A4] and according to the Magerl classification system [A3.1 vs. A3.2 vs. A3.3] as well as the extent of vertebral body comminution were significantly lower in patients with monosegmental ACR than in those with bisegmental ACR (Table 1)
Summary
In combined posterior–anterior stabilization of thoracolumbar burst fractures, the expandable vertebral body replacement device (VBRD) is typically placed bisegmentally for anterior column reconstruction (ACR). The VBRD is placed bisegmentally between the superior endplate of the caudad intact vertebra and the inferior endplate of the cephalad intact vertebra (bisegmental ACR, Fig. 1a) This results in fusion of two motion segments and requires partial resection of the fractured vertebral body (including the superior and inferior endplate) as well as of the adjacent cephalad and caudad intervertebral discs. In a substantial portion of burst fractures with significant vertebral body comminution, the inferior endplate is intact or shows a simple split fracture line only In this situation, the VBRD may be sufficiently anchored in the intact caudal part of the fractured vertebra and may be implanted monosegmentally between the inferior endplate of the fractured vertebra and the inferior endplate of the cephalad intact vertebra (monosegmental ACR, Fig. 1b). There are no studies to date that have systematically assessed the feasibility and outcome of monosegmental ACR using a VBRD in thoracolumbar burst fractures
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